British intelligence agency Government Communications Headquarters (GCHQ) reportedly intercepted the electronic communications of foreign politicians during G20 meetings that took place in London in 2009.

The agency used a series of techniques to intercept email, steal online login credentials and monitor the phone calls of foreign delegates who attended the meetings, U.K. newspaper The Guardian reported Monday. The G20 represents the top 20 economies of the world.

The newspaper claims that evidence of GCHQ's surveillance activity at the meetings was present in documents and PowerPoint presentations classified as top secret that were uncovered by Edward Snowden, a former intelligence contractor who recently leaked information about the U.S. National Security Agency's call metadata and electronic communication collection programs.

According to information from one document, GCHQ and U.K. intelligence service MI6 set up Internet cafes at the G20 meetings in order to extract key logging information and credentials from foreign delegates, giving the agencies "sustained intelligence options" against the targets even after the events ended.

The same document also mentions a particular tactic that involves the "active collection against an email account that acquires mail messages without removing them from the remote server" allowing the reading of people's emails before or at the same time as they do, The Guardian reported.

While it's not clear how exactly the key logging was done or how these Internet cafes were set up, the possibility of foreign delegates using public computers to check their email is not outside the realm of possibility, according to Bogdan Botezatu, a senior e-threat analyst at security vendor Bitdefender.

Back in 2009 the security landscape was different. Cyber-war was in its early days -- cyberespionage malware like Stuxnet, Flamer and others were active --but the public didn't know about them at the time, Botezatu said via email. There were no attacks from groups like Anonymous or LulzSec either, he said. "Shortly put, security standards were pretty low because there were no precedents."

One of the most common mistakes users do when they are in an official location is to presume that public computers and Internet connections are safe to use, Botezatu said.

While it's possible that some foreign delegates did use public computers to check their government-issued email accounts, it's more plausible that they forwarded official documents to their personal accounts for easy access while being away and checked those accounts instead, Botezatu said.

Downloading email messages from an account using an external email client and without deleting the messages from the server is not difficult, Botezatu said. "The most difficult part is actually the credential harvesting," he said.

It would have also been possible for GCHQ to perform real-time traffic sniffing on the network and read email messages as they were being accessed by the user, Botezatu said. Back in 2009, most webmail providers were only using SSL encryption for the initial authentication, not for the full session like many of them do today, he said.

Other secret documents reportedly seen by The Guardian described successful data interception efforts against BlackBerry smartphones that allowed GCHQ to provide advance copies of G20 briefings to U.K. ministers.

"Diplomatic targets from all nations have an MO of using smartphones. Exploited this use at the G20 meetings last year," one document said, according to The Guardian.

This could have either been done by sniffing Wi-Fi traffic originating from the phones or -- and this is less likely -- by obtaining the encryption keys from BlackBerry, formerly Research In Motion, Botezatu said.

According to an internal review, during the September 2009 meeting between the G20 finance ministers, GHCQ analysts were able to watch an automatically updated live graphic that was using telephone call records to show who was talking to whom at the conference, The Guardian said.

This report of GHCQ targeting foreign politicians at past high-level political meetings comes as political leaders from Canada, France, Germany, Italy, Japan, Russia, the U.S. and the U.K. meet for the 39th G8 summit in Enniskillen, Northern Ireland, starting Monday.